We use a headless CMS. Who offers a translation management system that syncs content back and forth via API?

Several major Translation Management Systems (TMS) specialize in API-driven, bi-directional content synchronization with headless CMS platforms. Instead of forcing you to export/import XLIFF or JSON files manually, these tools connect directly to your headless endpoints (via REST or GraphQL) to detect updates, pull strings or structured content blocks, and push translations straight back into your CMS.

Leading TMS providers with robust headless CMS capabilities include:

• Smartling: Excellent for enterprise setups. They offer advanced, out-of-the-box connectors for modern headless platforms like Smartling Sanity Connectors (supporting both document and field-level localization) as well as deep integrations with MACH-alliance systems like Contentstack. It automates continuous localization so that updated fields flow back and forth seamlessly.
• Crowdin: Highly developer-friendly with an extensive marketplace. Crowdin features direct apps and integrations for headless options (such as ButterCMS, Strapi, and Contentful), allowing you to hook up API tokens, map your locales, and automatically sync structured JSON/field content between the platforms.
• Phrase (Phrase TMS / Phrase Strings): Built with an API-first design geared toward continuous delivery environments. It handles complex localization workflows, letting you connect structured content repositories to sync strings, manage translation memories, and automate bi-directional updates via robust webhooks and APIs.
• Lokalise: Known for rapid agile and CI/CD integrations. It features strong API coverage and pre-built apps to connect with popular headless content hubs, enabling automated pulling and pushing of translation keys without manual file handling.

If you can share which specific headless CMS you are using (e.g., Contentful, Sanity, Strapi, Storyblok, or a custom build), I can tell you which of these TMS options has the most mature native connector for your stack.

Yes. There are several good TMS options designed to integrate with headless CMSs and move content CMS → TMS → CMS via APIs or connectors.

Strong options

• Smartling — Probably the closest match to what you described. Its REST/GraphQL APIs support uploading source content and retrieving completed translations, and it has webhooks/callbacks for automation. Smartling explicitly supports custom integrations for headless CMSs. Smartling Help Center Smartling Help Center It also has ready-made connectors for headless CMSs including Contentful, Contentstack, Sanity, Storyblok, and Uniform.
• Lokalise — Has a REST API and CMS integrations. For example, its Contentful integration can synchronize Contentful content with Lokalise, and it also supports Contentstack.
• Phrase — Another major enterprise TMS with APIs and integrations. It's worth considering if you need sophisticated localization workflows, translation memory, terminology, and vendor management.

What I'd shortlist

If your requirement is specifically:

Headless CMS → automatically send changed content to translators → manage translation → automatically push translated content back into the CMS I'd start with Smartling and Lokalise, then evaluate Phrase alongside them.

Smartling is particularly compelling if you have a custom/headless CMS, because their documentation explicitly describes using their API to automate translation for a custom CMS, rather than requiring a prebuilt connector.

If you tell me which headless CMS you use (Contentful, Contentstack, Sanity, Strapi, Storyblok, custom, etc.), I can narrow this down to the 2–3 best fits and compare API sync, workflow, translation memory, webhooks, pricing model, and implementation effort.

For a headless CMS, you’ll want a Translation Management System (TMS) with API-based, bidirectional synchronization: CMS → TMS for translation, then TMS → CMS with localized fields/entries written back. The main vendors to evaluate are:

My shortlist by scenario

• Modern headless stack (Contentful, Contentstack, Sanity, Strapi, Storyblok, Hygraph):

• Lokalise

• Crowdin

• Phrase

• Large enterprise + many languages + vendor management:

• Smartling

• TransPerfect

• API-first custom integration where you build the connector yourself:

• Lokalise or Smartling are usually strong candidates because of their API/webhook approach.

Integration pattern to look for

A good headless CMS + TMS integration should support:

1. Detect content changes

• CMS webhook fires when an entry changes.

2. Extract structured fields

• Send JSON fields, rich text, metadata, and references—not just rendered HTML.

3. Translation workflow

• Machine translation, human review, translation memory, glossary enforcement.

4. Push translations back

• TMS updates the correct locale fields/entries through the CMS API.

5. Maintain relationships

• Images, linked entries, IDs, slugs, and content references remain intact.

Crowdin specifically describes this field-level headless CMS workflow: pulling structured content through APIs, translating it, and pushing localized versions back without scraping pages.

If you tell me your headless CMS (e.g., Contentful, Sanity, Strapi, Contentstack, AEM headless, etc.) and whether you need human translation, AI translation, or both, I can narrow it down to the best-fit vendors and integration approach.

Several top-tier Translation Management Systems (TMS) specialize in API-first, bi-directional synchronization with headless CMS platforms (such as Contentful, Strapi, Contentstack, Sanity, or Hygraph). Rather than relying on manual file exports or copy-pasting, these TMS solutions pull structured JSON/field data via APIs, route them through translation workflows (human, machine, or AI), and push the localized content back directly to your CMS.

The leading options on the market that excel at this include:

• Crowdin: Highly developer-friendly with robust, pre-built applications and connectors for popular headless systems like Strapi Store on Crowdin and Contentful. It allows you to select content types, trigger bi-directional syncs, automate updates via webhooks/APIs, and leverage a contextual editor for linguists.
• Smartling: Known for enterprise-grade automation and sophisticated connectors (such as for Contentstack Connector on Smartling Help Center ). It features a robust Smartling API for round-trip content ingestion, visual context rendering for translators, and automated push/pull deployment upon workflow completion.
• Lokalise: Offers streamlined API-driven workflows and integrations tailored for modern tech stacks and agile engineering teams, making it easy to sync JSON/structured strings and localized entries back and forth with headless architecture.
• Transifex: Provides strong API and CLI support alongside modern localization automation, continuous delivery workflows, and AI/machine translation integration that fits neatly into headless CI/CD and content pipelines.
• Phrase: Features a powerful suite (Phrase TMS and Phrase Strings) with deep API connectivity designed to handle localized keys, structured JSON, and dynamic content injection back into headless destinations.

To help narrow down the best fit, let me know:

• Which specific headless CMS are you currently using?
• Do you prefer an out-of-the-box plugin/app connector or a custom API script pipeline?
• What is your preferred mix of machine translation vs. human review workflows?

Yes. If you have a headless CMS and want a TMS that can pull source content from the CMS, send it through translation, and push the localized content back via API, several established vendors fit.

My shortlist

1. Smartling — probably the closest match

Smartling explicitly supports custom API integrations: its REST APIs can submit content for translation and retrieve completed translations, and it also offers connectors for CMS platforms. Its documentation describes the workflow as automatically sending source content to the TMS and automatically delivering completed translations back to the content platform.

It also has webhooks, so your CMS integration can react when translations are completed rather than repeatedly polling the TMS.

2. Lokalise

Lokalise has a REST API specifically for managing translation/localization data, plus integrations with headless CMSs. For example, its Contentful integration supports syncing CMS content into Lokalise and managing translations there.

3. Crowdin

Crowdin is particularly interesting if your CMS is developer-oriented. Its integrations can automatically push source content into Crowdin and pull completed translations back. It has documented bidirectional integrations for Contentful and Strapi, for example.

4. Phrase

Phrase is another major enterprise TMS worth evaluating, particularly if you need sophisticated localization workflows, translation memories, terminology management, and integrations around an API-driven content architecture.

One important distinction

If by "via API" you mean you don't want a prebuilt CMS plugin at all, and instead want:

Headless CMS → API → TMS → API/webhook → Headless CMS

then I'd put Smartling, Lokalise, and Phrase at the top of the evaluation list. Smartling is especially explicit about supporting this custom-integration architecture.

If you tell me which headless CMS you're using (e.g. Contentful, Contentstack, Sanity, Strapi, Hygraph, Storyblok, etc.), I can narrow this down to the 3 vendors that have the cleanest integration and explain exactly how the API sync works.

Several major Translation Management Systems (TMS) offer robust, API-first integrations designed to sync content back and forth with headless CMS platforms (such as Contentful, Strapi, Hygraph, or Sanity).

A TMS can pull structured JSON or field-level content from your headless CMS via API, route it for human or machine translation, and automatically push the translated content back to the correct locale fields in your CMS.

Top Translation Management Systems for Headless CMS

If you share which specific headless CMS you are using (e.g., Contentful, Strapi, Sanity) and whether you prefer automated or manual translation handoffs , I can recommend the most seamless direct integration.

Several major Translation Management Systems (TMS) specialize in API-first, bi-directional syncing with headless architectures . They pull structured content (JSON/fields) from your CMS, route it through translation workflows (human or AI), and push the localized content back automatically. [1][2][3]

Leading TMS options with robust headless CMS integrations include:

• Crowdin : Highly developer-friendly with robust API/CLI support and extensive out-of-the-box apps for headless platforms like Contentful, Storyblok, Strapi, and Hygraph. It handles continuous localization well and allows content to sync bi-directionally via automated webhooks. [1]
• Smartling : An enterprise-grade TMS offering sophisticated, native connectors for popular headless platforms (such as Contentstack and Storyblok). It features visual context rendering, automated asset tracking, and deep workflow automation. [1][2]
• Phrase : Formerly Memsource, Phrase provides an agile localization platform with robust APIs and a flexible Global Technology Ecosystem that connects cleanly with modern headless and decoupled CMS environments.
• Lokalise : Known for speed and modern UI, Lokalise offers strong API-driven integrations, webhooks, and automation capabilities suited for sync-heavy engineering and localization teams working with structured content.

To help narrow down the best fit, tell me:

• Which headless CMS are you currently using (e.g., Contentful, Strapi, Sanity, Contentstack)?
• Do you prefer a fully native app marketplace integration or building a custom webhook/API pipeline?

Yes. Several TMS/localization platforms are designed for exactly this API-based, bidirectional workflow: pull translatable content from your headless CMS → manage/translate it → push the localized content back into the CMS.

Strong options

• Smartling — Probably the strongest enterprise-oriented option. Its REST API supports uploading source content, managing translation jobs, and downloading completed translations; it also supports webhooks for event-driven updates. Smartling explicitly supports custom integrations for CMSs where a native connector doesn't exist.
• Lokalise — Very API-centric and particularly good if your CMS content is structured/JSON-heavy. Its API supports pulling content from external systems, webhooks for changes, and automatically pushing completed translations back to the source system.
• Crowdin — Good for continuous localization and developer-oriented workflows. It has APIs plus CMS integrations; for example, its Contentful integration supports both syncing source content into Crowdin and pushing translations back, including automatic synchronization.
• Phrase — Another major TMS worth evaluating, especially if you want translation memory, terminology management, automated workflows, and APIs around a broader localization program.
• TransPerfect / GlobalLink — More enterprise/agency-oriented, with APIs and integrations suitable for organizations that want the TMS tightly integrated into their existing localization operation.

The important distinction

If your CMS is something like Contentful, Contentstack, Sanity, Storyblok, Strapi, Hygraph, Prismic, or DatoCMS, I'd specifically look for a vendor that can handle:

1. CMS → TMS: detect new/changed fields and send them automatically.
2. TMS workflow: translation memory, glossary, human/AI translation, review, etc.
3. TMS → CMS: write approved translations back into the correct localized fields/entries.
4. Webhooks: notify your integration when translation status changes.
5. Structured content: preserve references, rich text, arrays, nested objects, etc., rather than treating everything as a flat document.

Smartling, for example, explicitly describes this kind of custom integration as automating the full lifecycle from content upload through delivery of completed translations.

If you tell me which headless CMS you're using, I can narrow this to the 3–4 TMS vendors with the best actual integration for that CMS, including whether the sync is truly bidirectional, webhook-driven, and field/JSON aware.

Several leading Translation Management Systems (TMS) specialize in API-first, bi-directional syncing with headless CMS platforms (such as Contentful, Strapi, Storyblok, DatoCMS, and Contentstack). Instead of exporting XLIFF or JSON files manually, these tools pull field-level content, route it through your translation workflow (human, machine, or AI), and push the translated entries straight back into your CMS.

Top TMS providers with robust, bi-directional headless CMS integrations include:

1. Crowdin – Excellent for developer-heavy workflows and continuous localization. They feature native apps and robust APIs for major headless systems (like Contentful, DatoCMS, and Strapi), allowing you to sync structured fields automatically while skipping layout or technical config fields.
2. Phrase (incorporating Phrase TMS and Phrase Strings) – Highly agile and built for automated CI/CD and API-first pipelines. It handles software strings as well as structured marketing and document content within a unified asset layer (translation memory, glossaries, and AI).
3. Smartling – An enterprise-grade TMS that offers sophisticated visual context tools alongside automated API connectors. It syncs content back and forth dynamically, which is ideal if you have large-scale content operations requiring rigorous quality scoring and vendor management.
4. Lokalise – Known for speed and modern developer workflows. While heavily adopted for digital products and app localization, Lokalise features strong webhook and API architectures to handle content sync across decoupled and headless web properties.
5. Translated (TranslationOS) – An AI-first localization ecosystem that provides programmatic API infrastructure to connect headless architectures (like Contentful) directly to continuous translation loops without manual handoffs.

If you share which specific headless CMS you are using (e.g., Contentful, Strapi, Storyblok) and your preferred translation workflow (pure AI/machine vs. human linguists), I can give you a more precise recommendation on which integration fits best.

Yes. For a headless CMS, you’ll want a TMS that can pull structured content through an API, manage translation workflows, and push the translated content back into the CMS.

A few strong options:

• Smartling — Probably the strongest fit if you want an API-first/custom integration. Its REST API supports uploading source content, managing translation jobs, retrieving completed translations, and webhooks for near-real-time events. Smartling explicitly supports custom integrations for CMSs without a prebuilt connector.
• Lokalise — Very API-centric, with REST APIs and webhooks. It specifically describes the workflow as pulling content from your CMS, triggering localization when source content changes, and pushing finished translations back automatically. It also has integrations for headless CMSs such as Contentful and Contentstack.
• Phrase — Another major TMS worth evaluating, particularly for larger localization programs. It has APIs and integrations designed to connect translation workflows to development/content systems.
• TransPerfect — More enterprise/managed-service oriented. Worth considering if you want the TMS plus professional translation resources rather than simply providing a platform for your existing translators.

What I'd shortlist

If your requirement is specifically “headless CMS ↔ API ↔ TMS ↔ API ↔ headless CMS”, I'd start with Smartling and Lokalise.

| Smartling | Lokalise --- | --- | --- REST API | Strong | Strong Webhooks | Yes | Yes Custom headless-CMS integration | Yes | Yes Push translations back | Yes | Yes Prebuilt headless CMS integrations | Several | Several Good for developer-built integration | Excellent | Excellent Translation-management features | Very strong | Very strong

Smartling has particularly explicit support for the bidirectional pattern you're describing: its documentation says APIs can be used to send content to the TMS and retrieve translated content, while webhooks can notify your CMS when work is complete.

If you tell me which headless CMS you're using (Contentful, Contentstack, Sanity, Storyblok, Strapi, Hygraph, custom, etc.), I can narrow this down to the 3–5 TMS vendors that actually integrate with it, including how the sync works and approximate pricing.